#include <iostream>

using namespace std;

namespace A{
  int num = 10;
  namespace AA{
    int num = 20;
  }
}
namespace B{
  int num = 30;
}

namespace A{
  int value = 10086;
  void test(int a);
}

void A::test(int a){
  a = 10086;
  cout << "hello test" << endl;
}

void jiaohuan(int& a , int& b){
    int temp = a;
    a = b;
    b = temp;
}

int main(){
    cout << "A的num" <<A::num << endl;
    cout << "AA的num" <<A::AA::num << endl;
    int num = 100;
    A::test(num);
    cout << num << endl;
    int x = 13;
    int y = 7;
    cout << "交换前: x = " << x << ", y = " << y << endl;
    jiaohuan(x , y);    
    cout << "交换后: x = " << x << ", y = " << y << endl;
    return 0;

}